Hi Ana,

if you work on a study comparing groups or age effects, that analyzes 
hippocampal volume, then you would usually normalize that volume. People have 
different head sizes and therefore differently sized hippocampi. To remove 
headsize differences researchers often normalize voumes by ICV.

If you are interested in comparing the hippocampal volume between methods 
(manual and different automatic methods) and not between subjects, you do not 
need to normalize. ICV will be computed differently by different packages so 
you would just add more noise. Furthermore for your manual hippocampus labels 
you probably won't have manual ICV.

Best, Martin

On Oct 6, 2012, at 1:25 PM, Ana Arruda wrote:

> Thanks a lot Martin.
> 
> I really get confused about normalization. I've already done the comparisons 
> and the values between methods, as you said, are different. Although I 
> haven't understood why, in this case, I don't have to normalize. My advisor 
> told me to normalize all the brain values from the patients. Do you have any 
> idea what did he mean with that? I thought that this suggestion would be 
> related to hippocampus volume.
> 
> 
> Ana Arruda

---------------------------------
Dr. Martin Reuter
Assistant in Neuroscience - Massachusetts General Hospital
Instructor in Neurology   - Harvard Medical School
MGH / HMS / MIT

A.A.Martinos Center for Biomedical Imaging
149 Thirteenth Street, Suite 2301
Charlestown, MA 02129

Phone: +1-617-724-5652
Email: 
   mreu...@nmr.mgh.harvard.edu
   reu...@mit.edu
Web  : http://reuter.mit.edu 

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